Interpretation of susceptibility results

Results are reported as minimum inhibitory concentrations
(MICs), the minimum amount of drug needed to inhibit growth in
vitro. Interpretive criteria are based on achievable serum levels.
For certain antibiotics, the amount excreted into the urine via the
kidneys is above the MIC, and the agent is effective clinically in
this site even though reported as "resistant". Intermediate results
(I), especially for beta-lactam agents, indicate that doses higher
than standard recommendations may be effective. In other cases, "I"
results indicate that the organism may be susceptible or resistant
but the in vitro tests are not sensitive enough to determine
specifically. For this antibiogram, Intermediate results are NOT
included within the "%S" category.

Situations for which the use of vancomycin
is appropriate and acceptable

For treatment of serious infections due to
β-lactam-resistant gram- positive bacteria. Clinicians should be
aware that vancomycin is usually less active and less rapidly
bactericidal than β-lactam agents for organisms that are
susceptible to the β-lactams. Clinicians should also be aware that
vancomycin sensitive MIC 2mcg/ml is associated with increased
treatment failures.

For treatment of infections due to gram-positive organisms
in patients with serious allergy to β-lactam- antibiotics.

Prophylaxis, (infused 60-120 min before the first
incision), in penicillin- allergic patients, as recommended by the
Amer. Heart Assoc., for endocarditis following certain procedures
in patients at high risk for endocarditis. Cephalosporins are
still recommended for non-allergic patients.

Prophylaxis for major surgical procedures involving
implantation of prosthetic materials or devices, e.g., cardiac and
vascular procedures and total hip replacements, at institutions
with a high rate of infections due to MRSA or MRCoNS. Currently
MRSA and MRCoNS rates are 24% and 61% at SHC, respectively. A
single dose administered 60-120 min before surgery is sufficient
unless the procedure lasts more than 6 hours, in which case the
dose should be repeated. Prophylaxis should be dc'd after 2 doses
maximum.

Haemophilus influenzae

For infections with β-lactamase- producing H. influenzae:
cefuroxime, cefotaxime, trimethoprim/ sulfamethoxazole,
amoxicillin/clavulanate or azithromycin is recommended. Cefotaxime
or ceftriaxone is drug of choice for CNS infections. At Stanford,
74% of H. influenzae are ampicillin susceptible.